TC Kline Rear Spring Question

[02_lsb]

I have TCK DAs on my car. I recently dialed in the car a bit and the rear seems a bit soft. I am running 500# springs in the back. I am considering 700#.



The car is mainly used for weekend / cars and coffee duty. Am I going to ruin the ride?

[Tbonem3]

Possibly. For me, it was dependent upon isolating the stiffer spring well enough (with rubber).

The car will handle much better no matter what tho 🤙

[02_lsb]

Possibly. For me, it was dependent upon isolating the stiffer spring well enough (with rubber).

The car will handle much better no matter what tho 🤙

Elaborate please… alternative spring recommendations?

[Tbonem3]

Not the spring, what it sits on. Factory rubber pads are great, but even my homemade rubber donuts (1/8" & 3/16") have served me well.

My worst nvh experience was putting (only) 600lb eibach ers on metal ground control perch with just the gc polyurethane top cones (pretty hard themselves).

The rubber isolation is more important on top than below, on the control arm.

[bigjae46]

You should be fine with a 700# rear spring.

I run 450# front and 700# rear on TCK doubles. I've only run 700# rears and it can vary greatly depending on the damper setting. The rear gets really bouncy with the rebound and compression towards full soft. I've ran 600#, 500# and 400# fronts, the best ride so far has been the 400# springs. The only reason I went to a 450# spring is my front splitter would scrap in some places wit a 400# spring.

[02_lsb]

Thanks. I’ll call them on Tuesday.

I know for a while they were out of stock on those springs.

[cobra]

I'm running 630 rear springs and it's not uncomfortable necessarily but you definitely get less "compliance" which is more noticable on very uneven roads. Regular driving is less so.

[Tbonem3]

I will also say the damper is a major factor. My MCS with 343/628 is incredibly compliant with only firmness not harshness or noise.

[usdmej]

Am I going to ruin the ride?

Will chime in with my experience running 500/600/700 rears over the years

In general, 500 was great for street/canyon driving, 600 was on the firm side but kinda needed to stay competitive in autox especially on 200tw tires, 700 was pretty unbearable. The best shock in the world isn't gonna really matter when ur spring is so stuff it simply won't move over bumps

[bigjae46]

Thanks. I’ll call them on Tuesday.

I know for a while they were out of stock on those springs.

I'm going to try 900lb springs at some point. I know that's beyond the rear shocks but I'd like to try it first before I send the dampers in for a revalve.

I might be selling my 700lb rears...how soon do you need them?

[02_lsb]

I'm going to try 900lb springs at some point. I know that's beyond the rear shocks but I'd like to try it first before I send the dampers in for a revalve.

I might be selling my 700lb rears...how soon do you need them?

I don’t need them yesterday but I’d like to have them.. eventually. PM me.

[Tbonem3]

The best shock in the world isn't gonna really matter when ur spring is so stuff it simply won't move over bumps

Depends. Physics matter. 700lb for a grocery getter is different than a track car with aero doing 100mph.

[OldRanger]

I have Ohlins R&T (since April, when my focus shifted from daily driver to track HPDE). I’m using the Ohlins 400# spring front, and I just installed the TCK 700# spring. The ride height is 13 3/4” front and 13 1/8”rear. I have a also installed a Ground Control front sway bar set soft (about an inch from the end of the bar); I still have the OEM M3 rear bar. I have the Ohlins damper set at 6 from full firmm rear and 8 from full firm front.

I had only driven it on street since this change from the Ohlins springs and OEM bars. It’s a new feel.

My goal was to get less body roll in turns and rear pitching under acceleration. My car has to handle the weight of two people on the track (driver + instructor). I’ve already gutted the roof including sunroof delete and gutted the rear of the car to add a roll cage.

[usdmej]

Depends. Physics matter. 700lb for a grocery getter is different than a track car with aero doing 100mph.

Agree with that, I was assuming the guy wasn't running full aero and slicks (which would need a lot of spring rate and still be hell on street)

[bigjae46]

Agree with that, I was assuming the guy wasn't running full aero and slicks (which would need a lot of spring rate and still be hell on street)

I called TC Kline on the spring rate with aero vs non-aero question. He said that I was fine with 600/700 springs, didn't really get into the details why. Wish I did. I suspect that my springs are just stiff enough and his answer would have been different if I said 400/500lb springs.

I've been running aero with 400lb and 450lb front springs and no rear sway bar which is probably softer than anyone with a BMW on aftermarket springs/shocks runs. It does excellent in low speed turns, puts down the power really well and is really good in the high-speed turns. Its pretty amazing coming out of a low speed turn 40mph turn, I can pull on F8X M3s, ZL1s and GT3s (not slicks or hoosiers) on the exit for about the 1st quarter mile then they start running me down.

A 50-80mph turn is where my car or I am weakest. Which is apparent when I run track near DFW which mostly have those mid speed, trail brake turns. My theory is the car is kinda lazy from the extra compliance which is hurting and the aero hasn't really ramped up with the speed...or it could be the driver. I need some more time to really decide that. But the car feels significantly more planted and responsive turning in at 120mph than it does at 75mph.

Its all about trade offs. With higher spring rates and aero you lose some mechanical grip so you lose some speed in low speed turns and exit speed. That will help you at one track and could hurt you at another. I could run stiffer springs at the DFW tracks (smoother, mid-speed turns) but then I think it would be less optimal at my home track in Houston (bumpy, low and high speed turns).

This is all on Toyo RRs and NT01s. If I run stickier tires, I need stiffer springs to take advantage of them. Which is where I am at now - I need to either upgrade my dampers or rebuild my TCKs to handle higher spring rates. I'm leaning towards a rebuild. Everyone goes with MCS and I like to be different.